Dual-Switch Valve Research Articles

Considerations in the Use of Gravitational Valves in the Management of Hydrocephalus. Some Lessons Learned with the Dual-Switch Valve.

In the past decade, there has been a clear trend towards better outcomes in patients with hydrocephalus, especially those with normal pressure hydrocephalus (NPH). This is partly due to the availability of more sophisticated hardware and a better understanding of implants. However, there is little evidence to show the superiority of a specific type of valve over another. The most commonly reported consequence of hydrodynamic mismatch is shunt over-drainage. Simple differential pressure valves, with a fixed opening pressure or even adjustable valves, lead to non-physiologic intraventricular pressure (IVP) as soon as the patient moves into an upright posture. These valves fail to maintain IVP within physiological limits due to the changes in hydrostatic pressure in the drainage system. To solve this problem more complex third-generation hydrostatic valves have been designed. These gravitational devices aim to reduce flow through a shunt system when the patient is upright but there are important technical differences between them. Here we review the main characteristics of the Miethke® Dual-Switch valve, which includes two valve chambers arranged in parallel: a low-opening pressure valve, designed for working in the supine position, and a second high-opening pressure valve, which starts working when the patient assumes the upright position. This paper specifies the main advantages and drawbacks of this device and provide a series of recommendations for its use. The discussion of this specific gravitational valve allows us to emphasize the importance of using gravitational control in implanted shunts and some the caveats neurosurgeons should take into consideration when using gravitational devices in patients with hydrocephalus. The correct function of any gravitational device depends on adequate device implantation along the vertical body axis. Misalignment from the vertical axis equal to or more than 45° might eliminate the beneficial effect of these devices.

Miethke DualSwitch Valve in lumboperitoneal shunts

Despite the existence of wide variety of shunt systems, physiological regulation of intracranial pressure in shunted patients remains a utopian dream. Lumboperitoneal shunts (LPS) have long been used for treating idiopathic intracranial hypertension and other types of "communicating" hydrocephalus. Although they can provide rapid and effective symptom resolution, cerebrospinal fluid (CSF) over-drainage remains a common complication of LPS. We introduce the use of the Miethke DualSwitch Valve (M-DSV) for LPS and describe our preliminary experience with these valves in managing and avoiding CSF over-drainage. This is the first description of the use of M-DSV for LPS. Over 6 months, we treated five patients with LPS using M-DSV. Prior to the use of the M-DSV, four patients experienced significant over-drainage symptoms secondary to LPS. Data was collected prospectively, including preoperative details and clinical outcome. Five patients (age range, 22 to 71 years) were operated upon. Three patients had pseudotumor cerebri, one patient had an LPS for treatment of a posterior fossa pseudomeningocele, and one had an LPS for treatment of cauda equina syndrome secondary to lumbar dural ectasia. Four patients had a history of clinical over-drainage secondary to pre-existing LPS systems. The fifth patient had an LPS revision after the previous LPS migrated. Follow-up ranged from 5 to 11 months (mean, 7.8 ± 3 months). All patients had a good outcome with immediate resolution of over-drainage symptoms and are currently asymptomatic. The use of M-DSV in LPS is an effective alternative for avoiding posture-related over-drainage and managing patients with LPS-related over-drainage symptoms. Further experience is required to address the long-term outcome, balancing sufficient drainage while preventing over-drainage.

O.102 Posterior fossa lesions: Treat the disease not hydrocephalus

Especially in patients with normal pressure hydrocephalus (NPH), conventional differential-pressure valves are known to create nonphysiological negative intraventricular pressure values (IVP) when the patient moves into the upright position, with the consequence of numerous, sometimes severe, complications. The recently presented gravitational devices promise improvement, primarily in respect to this disadvantage.In a prospective multicenter study the new Miethke dual- switch valve (DSV) has been implanted in 128 patients with NPH. The patients have been assessed before operation, at discharge, and re-evaluated 6 to 9 months after surgery. The technical principle of the new device is presented.The clinical follow-up showed excellent results in 63% of the patients, satisfactory results in 16%, and a bad outcome in 21% of the cases. The infection rate was 5%; the rate of mechanical complications including overdrainage and dislocations has been in total 9%, and underdrainage was suspected in 7 cases. The outcome correlated with the preoperative severity of NPH. Despite the clinical outcome, the computed tomography scans showed only minimal or no reduction of the ventricular size in the majority of cases. We found a valve-related rate of overdrainage of 2.5%, which is clearly lower than results of comparable series in the literature.The clinical course of patients suffering from NPH is mainly influenced by the stage of the disease, the time of beginning of the therapy, and the gravitational function of the implanted device. Based on our clinical experiences with the Miethke dual-switch valve (MD-SV), we underscore the advantages of this valve for the treatment of hydrocephalus, especially for patients with NPH.

Clinical Experience With a Dual Switch Valve (Miethke) for the Management of Adult Hydrocephalus

The dual switch valve (DSV), which switches between two parallel valve chambers depending on the patient posture, was evaluated in 101 consecutive adult patients with hydrocephalus who required shunt surgery. The opening pressure was 5 or 10 cmH(2)O for the supine position and 30 or 40 cmH(2)O for the upright position depending on the sitting height. The results clearly showed that the DSV can regulate the intraventricular pressure (IVP) to 5 to 10 cmH(2)O in the supine and almost zero in the upright position, independently of posture. Ninety-four of the 101 patients received the DSV and 86 patients showed some clinical improvement. However, three patients required irrigation of subdural hematoma and six were thought to suffer underdrainage (4 probable and 2 possible). Such underdrainage probably resulted from the relatively high opening pressure in the supine position of 10 cmH(2)O and the bedridden state of these patients. This problem may be solved by the DSV with the 5 cmH(2)O setting in the supine position. The DSV can maintain physiological IVP in hydrocephalic patients independently of posture and provides generally satisfactory clinical outcome, but cannot prevent all inadequate drainage-related problems.

Predictors of Outcome in Patients with Normal-Pressure Hydrocephalus

Despite emerging knowledge of over 40 years, the postoperative results after shunt implantations in patients diagnosed for normal-pressure hydrocephalus (NPH) have not improved significantly in the last decade. For this reason, predictors have to be identified in order to preoperatively predict the course of disease. From 1982 to 2000, we examined in a prospective study 200 patients diagnosed for NPH. Of the patients who were surgically treated by a shunt implantation we could re-examine 155 (78%) in a mean time interval of 7 months after operation. The NPH was graduated according to the results of the intrathecal infusion test in an early state NPH (without brain atrophy) and late state NPH (with brain atrophy). In the study we focused our attention on the possible predictors: patient’s age, length of disease, clinical signs – like gait ataxia, dementia and bladder incontinence, etiology idiopathic/secondary as well as implanted valve type and the value of resistance to cerebrospinal fluid outflow. To measure the outcome we used the NPH recovery rate, as statistical test the χ² according to Pearson. In 80 patients with an early stage NPH (without cerebral atrophy) and a short course of disease (<1 year), slightly distinct dementia and an implanted Miethke Dual-Switch valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only a minimal relevance for the outcome. Those 75 patients with a late state NPH (with cerebral atrophy) had a better outcome when dementia was not present, the outflow resistance was >20 mm Hg·min/ml, the CSF tap test was positive and a Miethke Dual-Switch valve was implanted.

Evaluation of the Miethke dual- switch valve in patients with normal pressure hydrocephalus

Objective Especially in patients with normal pressure hydrocephalus (NPH), conventional differential-pressure valves are known to create nonphysiological negative intraventricular pressure values (IVP) when the patient moves into the upright position, with the consequence of numerous, sometimes severe, complications. The recently presented gravitational devices promise improvement, primarily in respect to this disadvantage. Methods In a prospective multicenter study the new Miethke dual- switch valve (DSV) has been implanted in 128 patients with NPH. The patients have been assessed before operation, at discharge, and re-evaluated 6 to 9 months after surgery. The technical principle of the new device is presented. Results The clinical follow-up showed excellent results in 63% of the patients, satisfactory results in 16%, and a bad outcome in 21% of the cases. The infection rate was 5%; the rate of mechanical complications including overdrainage and dislocations has been in total 9%, and underdrainage was suspected in 7 cases. The outcome correlated with the preoperative severity of NPH. Despite the clinical outcome, the computed tomography scans showed only minimal or no reduction of the ventricular size in the majority of cases. We found a valve-related rate of overdrainage of 2.5%, which is clearly lower than results of comparable series in the literature. Conclusion The clinical course of patients suffering from NPH is mainly influenced by the stage of the disease, the time of beginning of the therapy, and the gravitational function of the implanted device. Based on our clinical experiences with the Miethke dual-switch valve (MD-SV), we underscore the advantages of this valve for the treatment of hydrocephalus, especially for patients with NPH.

The enigma of underdrainage in shunting of hydrocephalus

Materials and Methods In a series of 202 patients of different etiologies treated with the hydrostatic Dual-switch-valve (DSV), 22 cases were suspected of suffering from underdrainage. Using a new algorithm to differentiate between different causes of mechanical obstruction on the one hand and functional underdrainage, we saw an indication to exchange the DSV to one with a lower opening pressure in 15 cases.

Five years experience with gravitational shunts in chronic hydrocephalus of adults.

Gravitational shunts for management of chronic hydrocephalus are supposed to avoid or at least to reduce the risk of overdrainage. In order to find out if this hypothesis is correct, we did a prospective study and analysed the results of a series of 185 hydrocephalic adults, treated by using gravitational shunts. For the few cases in whom overdrainage occurred, we wanted to establish the reason for it. Especially it should be proven or excluded that overdrainage was caused by shortcomings of the principle of gravitational shunts. Another goal was to compare post-shunting changes of the ventricular size with clinical outcome. A comparably large study has not yet been published. 185 adult patients who suffered from chronic hydrocephalus were shunted between 1996-2000, either using the combination of an adjustable Codmann Hakim Valve & Miethke Shunt Assistant (35 patients) or a Miethke Dual Switch Valve (150 patients). The clinical course of each patient has been followed until the end of 2000. Average follow-up time was 26 months (range 6-60 months). 88% of our patients were shunt responders, 70% had a good or excellent outcome. Overdrainage occurred in only 4%. It turned out that this complication was not a failure of the concept of gravitational shunts, but the result of a wrongly estimated intraperitoneal pressure. After shunting the ventricular size was reduced only marginally. In 92% of the patients the Evans-Index decreased less than 20% after the shunt insertion, but 69% of these patients had a good or excellent outcome. The most obvious difference comparing pre- and postoperative imaging was a better visibility of the high apical sulci after shunting. In our series gravitational shunts proved to be effective in preventing overdrainage. The 4% negative exceptions are mainly avoidable. There was no correlation between outcome and ventricular size reduction, and as a rule ventricular size was only marginally reduced.

The Miethke Dual-Switch Valve in Patients With Normal Pressure Hydrocephalus

Especially in patients with normal pressure hydrocephalus (NPH), conventional differential pressure valves are known to create unphysiologic negative intraventricular pressure values when the patient moves to an upright position, with the consequence of numerous and sometimes severe complications. The recently presented gravitational devices promise improvement primarily with respect to this disadvantage. In a prospective multicenter study, the new Miethke Dual-Switch Valve (DSV) was implanted in 128 patients with NPH. The patients were assessed before surgery and at discharge, and they were re-evaluated 6 to 9 months after surgery. The technical principle of the new device is presented. The clinical follow-up showed excellent results in 63% of the patients, satisfactory results in 16%, and a poor outcome in 21%. The outcome correlated with the preoperative severity of NPH. Despite the clinical outcome, the computed tomography scans showed nearly no or only a minimal reduction of the ventricular size in most cases. We found a valve-related rate of overdrainage of 2.5%, which is clearly lower than the results of comparable series in the literature. The clinical course of patients suffering from NPH is mainly influenced by the stage of the disease, the time of beginning the therapy, and the gravitational function of the implanted device. Based on our clinical experiences with the Miethke DSV, we underline the advantages of this valve for the treatment of hydrocephalus, especially for patients with NPH.

Pitfalls in shunting of hydrocephalus—Clinical reality and improvement by the hydrostatic dual-switch valve: C. Sprung, C. Miethke, K. Shakeri, et al. Eur J Pediatr Surg 8:26–30, (December), 1998 (suppl I)

Pitfalls in shunting of hydrocephalus—Clinical reality and improvement by the hydrostatic dual-switch valve: C. Sprung, C. Miethke, K. Shakeri, et al. Eur J Pediatr Surg 8:26–30, (December), 1998 (suppl I)

O-29-428 - Clinical experience with the hydrostatic dual-switch valve

Soil solarization was applied for 60 days during the summer in lettuce fields in Mogi das Cruzes (latitude 22°31′S, longitude 48°11′W), southeastern Brazil, from December to January, 1998/99 and 1999/2000, after which two consecutive lettuce crops were grown in each cropping season. Soil solarization was tested in association with the fungicides pencycuron and procymidone, with the purpose of controlling bottom rot and lettuce drop, caused by Rhizoctonia solani AG1-I and Sclerotinia minor, respectively. In the first crop of both years the solarized treatments presented very low incidences of the diseases and shortened the crop cycle by 10 days as compared to the non-solarized plots. In both years the incidence of lettuce drop in the second (winter) crops was very low in the solarized plots, but a 25–40% loss of lettuce heads to the disease was observed in the control plots (no solarization and no fungicides). Although the incidence of diseases in the non-solarized plots was reduced by the fungicides, they did not offer additional benefits in the solarized areas in both crops. Reductions in biomass C and in the number of fungi and bacteria were observed in the solarized treatments, but the amount of fluorescent pseudomonas was not affected by the soil treatments. The concentrations of soil nutrients NH4–N and DTPA-extractable-Mn increased sharply due to solarization. Changes in soil nutrient availability and probably in the microbial community, among other non-detected benefits, may be related to the reduction of the crop cycle in the present work.